Tunable magnetron oscillator



Jan. 12, 1954 F. HUTCHINSON 2,666,165 TUNABLE MAGNETRON OSCILLATOR FiledJan. 3, 1946 ISM \ l7 K p 7 rN/i?! -5 6 A0 I0 I j INVENTOR FRANKLINHUTCHINSON BY ATTORNEY Fate-med Jan. 12, 1954 TUNABLE MAGNETRONOSCILLATOR Franklin Hutchinson, New Haven, Conn, assignor, by mesneassignments, to the United States of America. as represented by theSecretary of War Application January 3, 1946, Serial No. 638,883 r 7Claims. (01. 315-40) My invention relates in general to electricalapparatu and more particularlyto magnetron oscillators.

In the art of ultra-high frequency and mlcro- Wave energy generation bymeans of magnetron oscillators it is often desirable to couple auxiliaryresonant devices to a magnetron in order to effect stabilization of, orcontrolled alteration in, the fre uency of the generated oscillations.Where the individual resonators of a multi-cavity magnetron are strappedtogether, as is frequently the case, it is possible to couple externalapparatus very tightly to the magnetron through the straps.

Previously, such coupling has always necessitated mechanical attachmentof one or more leads to the straps of the magnetron. If the points ofattachment are not symmetrically located on the straps, it has beenfound that angular distortion of the radio-frequency fields in theelectronic interaction space results, with possible impairment ofperformance. Furthermore, in the upper rang of frequencies in use at thepresent time it becomes increasingly difiicult to make lead connectionsto the straps because of the extremely small dimensions of the magnetroncomponents.

Accordingly, it is one object of my invention to provide means ofcoupling to a magnetron.

Another object is to provide means of symmetrically coupling to astrapped magnetron.

Still another object is to provide a readily adjustabl means of couplingto a magnetron.

Yet another object is to provide means of coupling to the straps of amagnetron without making mechanical attachments to the straps.

A further object is to provide a tunable magnetron oscillator.

A still further object is to provide a novel tuning or stabilizationcavity for a magnetron oscillator.

Briefly, my invention accomplishes these and other objects which will beapparent to those skilled in the art by utilizing capacitive couplingbetween the magnetron straps and a disk-like member aligned in a planeparallel thereto. A rod attached to the disk passes into a cavityresonator constructed within one of the pole pieces of the magentronmagnet. A coaxial line composed of the rod and the pole piece connectsthe resonator and the disk.

The principles and operation of my invention will be more apparent uponreference to the following specification, claims, and to the drawing,the single figure of which represents a cross- 2 sectional view of amagnetron and tuning apparatus therefor.

Referring now to this figure, a standard multicavity magnetron anode 5and cathode 6 are shown. Anode 5 is double-strapped at both ends withrings 7, 8, 5, and Ill. The magnetic field for the magnetron is suppliedby a magnet the pole pieces l2 and 13 of Which are shown. Pol piece I3is hollowed. out to form a cavity resonator l4 and a sliding plug [5 isinserted therein. A rod It extends through plug l5, being supported byth plug and by a glass member ll which is not sealed to the rod it butis sealed to a sleeve I8, the latter being preferably of the alloy knownby the trade name Kovar, and which in turn is seated in pole piece l3.Rod [6, then passes through a hole l9 bored in pole piece l3 and at theextremityof the rod is attached a circular plate 26, the periphery ofwhich extends farther toward the magnetron straps than does the center..The disk is substantially the diameter of strap 8.

In the operation of the device the inherent capacity between strap 8 andplate 20 couple oscillatory energy into the coaxial conductor formed bypole piece 13 and rod l6. Glass seal I! does not inhibit the passage ofenergy into resonant cavity I l, hence oscillations are set up therein.The resonant frequency of cavity I4 is readily adjusted by sliding plugl5 toward or away from the magnetron anode. Hence the magnetron may betuned within a predetermined bands of frequencies. The degree ofcoupling between the resonant cavity and the magnetron is governed bythe spacing between plate 20 and strap 8. This spacing may be varied bysliding rod l6 toward or away from the magnetron anode. This variabilityis valuable in practice since the degree of coupling can be heldconstant despite unavoidable variations in the dimensions of the Variousparts of the assembly.

The cavity resonator I4 is not the only possible frequency determiningmeans nor is a coaxial line necessary to conduct energy from disk 20.The auxiliary resonator may, for example, be a resonant section oftransmission line or a cavity resonator external to the apparatus, andthe connector may be a single wire directly attached to the energypick-up means and run out through the side of the device. Indeed, it isfeasible to use a pick-up other than disk-shaped, as long as there issuflicient capacity between strap 8 and th pick-up to provide adequatecoupling. However, in practice a disk which may be spaced apart 3 fromthe strap between 0.005 and 0.020 inch has been found satisfactory.

It will be understood that what has been described hereinbefore is apreferred embodiment of my invention but adaptations and modificationsmay be made therein Without departure from the principles of myinvention. 2581166,.1 claim all such modifications and adaptations asmay fall fairly Within the spirit and. scope of the hereinafter appendedclaims.

What is claimed is:

1. In a magnetron oscillator a segmented anode electrode, at least one:strip of conducting material joining at least aportiorr-ofsaidranode'segments, a conducting memberin spaced rela tionship with respect tosaid anode electrode and.

which is movably positioned adjacentlto saidzcone ducting strip, saidconducting member, being capacitively coupled to said conducting strip?a; cavity resonator, and means coupling said conducting member to: saidcavity resonator whereby the frequency of oscillations createdir-rsaid'magnetron oscillator is determined by the resonant frequency ofsaid cavity resonator.

2. In a magnetron oscillator a segmentedanode electrode, a ring-likeconducting member joining at leasta portion of said anc'd-esegments; a--movable circular conducting member of substantiaily the same diameter assaid ring-like member in spaced relationship with respect to said anode.electrode: and which is positioned adjac ent to said ring-like member, acavity res onator, and means coupling sai'd circular member to saidcavity resonator whereby "the frequency' of oscillations generated bysaid magnetronoscillator is determined by: the resonantfrequency ofsaid" cavity resonator;

3% Apparatus in accordance with claim 2 wherein in addition there isprovided a magnet positioned adjacent to said anodeelectrode; one of thepoles of said magnet'being chambered to form said cavity resonator.

4'. Apparatus in accordance with 0mm 2 further including meansmovableinto said cavityresonator for tuning said cavity resonator,therebyenabling the frequency of oscillation of" said magnetron to" bevaried in a predetermined fashion;

5. A magnetron oscillator comprising a. segmented anode electrode, a.ring-like strap con- 7 Number Name Date 21631589 Dallenbaeh et a1. "aJune 27, 1939" 2,233,166 Hahn Feb. 25,. I941" 2308,2135 Q Spencer Sept.24', 1946 23408238 Sp'e'n'ce'r Sept. 24'', I946. 2,411,953? B'roW'n Dec.31,1946 2,414,085 Hartman Jan. 14, I947 2,421,639 McArthur June 3, I947214241496 Nelson July 22; 1947 2,466,060 Spencer Apr; 5", I9492,466,765" Hartman Apr; I2, 1949 2,482,541" Hall etal Sept. 20", I9492,542,399" Brown Feb. 20, I951,

4 nected to at least a portion of said anode segments, a disk-likemember in spaced relationship with respect to said anode electrode,means movably positioning said disk-like member adjacent to said strapso that said disk-like member remains symmetrical to said strapthroughout the entire range of? its movement and electrical changesinsaid strap produce corresponding changes in said disk-like memberthrough the capacity therebetween, a tunable cavity resonator, and meansextending through a Wall of said cavity resonator coupling said cavityresonator only to:said disk-like member, said cavity resonatorbeingcompletely closed except for said coupling means extendingtherethrough.

6. In a magnetron oscillator, a segmented anode electrode}, a ring-likemember joining at least a portion of said anode segments, a disklikemember of substantially the same diameter as said ring-like member, saiddisk-like member being arranged concentrically with said ringf-likemember and in spaced relationship with respect to said anode electrode,whereby electrical changes in said ring-like member are: transferred tosaiddisk-like: member through: the inherent capacity therebetween acavity res'0- na-tor, and meanscouplin'g said cavity resonator to saiddisk-lilac member; said cavity resonator being completely enclosedexcept-for an. opening for said coupling means; 7

7 The-magnetron oscillator defined in claim- 6, further including meansm'ovable intosaid cavity resonator fortun'ingsai'd cavityresonator.

FRANKLIN HUTCHINSON- References Cited. in the file of this patentUNITED- PATENTS

